Keep flounder cool on the trip from the market to your house. Never let it stay unrefrigerated for long. To store flounder, remove packaging, rinse the fish under cold water, and pat dry with paper towels. Fish deteriorates when it sits in its own juices, so place it on a cake rack in a shallow pan filled with crushed ice. Cover with cling wrap or foil and set in the coldest part of the refrigerator. Flounder will store well this way for up to two days. When well-wrapped, flounder can be frozen for up to two months in a refrigerator and for three to four months in a deep-freeze. Using lined freezer paper, wrap the fish tightly from head to tail with at least two layers of paper. To thaw the fish slowly, unwrap, place in a pan, cover, and leave for 24 hours in the refrigerator. To thaw more quickly, place the whole fish, wrapped in a watertight bag, in a sink with cool running water, allowing about 30 minutes per pound (450g). For fastest thawing, use the defrost cycle of your microwave, allowing two to five minutes per pound (450g) with equal standing time in between zaps (as one minute defrost to one minute resting).